call scale only when point has it

Author: tomato42

src/ecdsa/keys.py

@@ -724,7 +724,8 @@ def from_secret_exponent(cls, secexp, curve=NIST192p, hashfunc=sha1):
                 "Invalid value for secexp, expected integer between 1 and {0}"
                 .format(n))
         pubkey_point = curve.generator * secexp
-        pubkey_point = pubkey_point.scale()
+        if hasattr(pubkey_point, "scale"):
+            pubkey_point = pubkey_point.scale()
         self.verifying_key = VerifyingKey.from_public_point(pubkey_point, curve,
                                                             hashfunc, False)
         pubkey = self.verifying_key.pubkey